So far, there have been many proposals concerning catalysts for use in producing unsaturated aldehydes and unsaturated carboxylic acids through gas-phase catalytic oxidation of propylene, isobutylene, TBA or MTBE and methods for producing such catalysts.
Most of such catalysts have a composition containing at least molybdenum, bismuth and iron and molded catalysts having such a composition are industrially used. These catalysts are classified into an extrusion-molded catalyst, a supported catalyst or the like depending on their methods of molding. Normally, the extrusion-molded catalyst is produced through the steps of kneading particles containing catalyst components and molding the resultant kneaded mixture.
In Patent document 1, a method of adding a certain cellulose derivative when a catalyst is extrusion-molded is disclosed. Further, in Patent document 1, it is disclosed that a cellulose derivative having a viscosity of its 2% water solution in the range of 1,000 to 10,000 cps at 20° C. is used, and when the viscosity exceeds 10,000 cps, an extrusion moldability of the material to which the cellulose derivative has been added becomes deteriorated and there is little effect on the improvement of the moldability.
Further, in Patent document 2, a method for producing an extrusion-molded catalyst is disclosed, wherein two kinds of binder, namely, hydroxypropyl methylcellulose and curdlan are used, and it is further disclosed that as a cellulose derivative which can be used as a molding aid, one having a viscosity of its 2% water solution in the range of 1,000 to 10,000 mPa·s at 20° C. is preferable because of the good moldability.
However, catalysts obtained by these publicly known methods are not always sufficient as an industrial catalyst in respect of catalyst activity, selectivity to a target product and the like and hence a further improvement has been generally desired from the industrial point of view.
Patent document 1: Japanese Patent Application, First Publication No. Hei 7-16,464
Patent document 2: Japanese Patent Application, First Publication No. 2002-282,695